X-Git-Url: https://git.decadent.org.uk/gitweb/?p=nfs-utils.git;a=blobdiff_plain;f=utils%2Fmount%2Fnfs.man;h=d92da1905a74a64cdc882e93ac90176abcacce52;hp=ad44d71590ff4c8f11d9ab6dd0c671b0e13ae0e1;hb=19517eaaa68af5f299157d07186defa383a18e88;hpb=16db99b56a532bf56fa27618a6ef30763cd9006f diff --git a/utils/mount/nfs.man b/utils/mount/nfs.man index ad44d71..d92da19 100644 --- a/utils/mount/nfs.man +++ b/utils/mount/nfs.man @@ -24,15 +24,16 @@ To mount via NFS version 2, use the .BR nfs file system type and specify .BR nfsvers=2 . -Version 2 is the default protocol version for the -.BR nfs -file system type when -.BR nfsvers= -is not specified on the mount command. To mount via NFS version 3, use the .BR nfs file system type and specify .BR nfsvers=3 . +Version 3 is the default protocol version for the +.BR nfs +file system type when +.BR nfsvers= +is not specified on the mount command and both client and server +support it. To mount via NFS version 4, use the .BR nfs4 file system type. @@ -45,8 +46,8 @@ file system type. These file system types share similar mount options; the differences are listed below. .P -Here is an example from an \fI/etc/fstab\fP file for an NFSv2 mount -over UDP. +Here is an example from an \fI/etc/fstab\fP file for an NFSv3 mount +over TCP. .sp .nf .ta 2.5i +0.75i +0.75i +1.0i @@ -194,8 +195,18 @@ many other operating systems. .TP 1.5i .I nolock Disable NFS locking. Do not start lockd. -This has to be used with some old NFS servers +This is appropriate for mounting the root filesystem or +.B /usr +or +.BR /var . +These filesystems are typically either read-only or not shared, and in +those cases, remote locking is not needed. +This also needs to be used with some old NFS servers that don't support locking. +.br +Note that applications can still get locks on files, but the locks +only provide exclusion locally. Other clients mounting the same +filesystem will not be able to detect the locks. .TP 1.5i .I bg If the first NFS mount attempt times out, retry the mount @@ -266,12 +277,34 @@ Note that there is a performance penalty when using integrity or privacy. .TP 1.5i .I tcp -Mount the NFS filesystem using the TCP protocol instead of the -default UDP protocol. Many NFS servers only support UDP. +Mount the NFS filesystem using the TCP protocol. This is the default +if it is supported by both client and server. Many NFS servers only +support UDP. .TP 1.5i .I udp -Mount the NFS filesystem using the UDP protocol. This -is the default. +Mount the NFS filesystem using the UDP protocol. +.TP 1.5i +.I nordirplus +Disables NFSv3 READDIRPLUS RPCs. Use this option when +mounting servers that don't support or have broken +READDIRPLUS implementations. +.TP 1.5i +.I nosharecache +As of kernel 2.6.18, it is no longer possible to mount the same +same filesystem with different mount options to a new mountpoint. +It was deemed unsafe to do so, since cached data cannot be shared +between the two mountpoints. In consequence, files or directories +that were common to both mountpoint subtrees could often be seen to +be out of sync following an update. +.br +This option allows administrators to select the pre-2.6.18 behaviour, +permitting the same filesystem to be mounted with different mount +options. +.br +.B Beware: +Use of this option is not recommended unless you are certain that there +are no hard links or subtrees of this mountpoint that are mounted +elsewhere. .P All of the non-value options have corresponding nooption forms. For example, nointr means don't allow file operations to be @@ -378,11 +411,23 @@ Valid protocol types are and .IR tcp . .TP 1.5i -.I clientaddr=n -On a multi-homed client, this -causes the client to use a specific callback address when -communicating with an NFS version 4 server. -This option is currently ignored. +.I clientaddr=n.n.n.n +Specifies a single IPv4 address in dotted-quad form that +the NFS client advertises to allow servers to perform +NFSv4 callback requests against files on this mount point. +If the server is not able to establish callback connections +to clients, performance may degrade, or accesses to +files may temporarily hang. +.IP +If this option is not specified, the +.BR mount (8) +command attempts to discover an appropriate callback +address automatically. +The automatic discovery process is not perfect, however. +In the presence of multiple client network interfaces, special +routing policies, or atypical network topologies, the exact +address to use for callbacks may be nontrivial to determine, +and should be explicitly set using this mount option. .TP 1.5i .I sec=mode Same as \f3sec=mode\f1 for the nfs filesystem type (see above). @@ -428,6 +473,23 @@ This extracts a server performance penalty but it allows two different NFS clients to get reasonable good results when both clients are actively writing to common filesystem on the server. +.TP 1.5i +.I nosharecache +As of kernel 2.6.18, it is no longer possible to mount the same +same filesystem with different mount options to a new mountpoint. +It was deemed unsafe to do so, since cached data cannot be shared +between the two mountpoints. In consequence, files or directories +that were common to both mountpoint subtrees could often be seen to +be out of sync following an update. +.br +This option allows administrators to select the pre-2.6.18 behaviour, +permitting the same filesystem to be mounted with different mount +options. +.br +.B Beware: +Use of this option is not recommended unless you are certain that there +are no hard links or subtrees of this mountpoint that are mounted +elsewhere. .P All of the non-value options have corresponding nooption forms. For example, nointr means don't allow file operations to be @@ -439,14 +501,6 @@ interrupted. .SH AUTHOR "Rick Sladkey" .SH BUGS -The posix, and nocto options are parsed by mount -but currently are silently ignored. -.P -The tcp and namlen options are implemented but are not currently -supported by the Linux kernel. -.P -The umount command should notify the server -when an NFS filesystem is unmounted. .P Checking files on NFS filesystem referenced by file descriptors (i.e. the .BR fcntl